This invention relates generally to positioning guides for dental implants, and to techniques for locating the placement of dental implants. The positioning guides may also be called parallel pins, placement guides, angulation indicators, dental guides and surgical guides.
People who are lacking an entire tooth and root structure for one or more teeth may receive prosthetic replacements. These replacements may include an implant that is surgically secured to the jawbone. An abutment may engage the implant and extend above the gum or gingival tissue. A natural looking artificial tooth crown may then be secured to the abutment. In many cases, the prosthetic device is indistinguishable from a natural tooth. In this way, people who are edentulous (for example, because they have lost the entire tooth structure) can receive one or more prosthetic replacements.
It may not always be possible to position the implant and the prosthetic tooth in precise vertical alignment. This inability to achieve a vertical orientation can occur for a number of reasons. Most obviously, the patient's natural teeth may not permit such a vertically aligned orientation. Of course, the prosthetic replacement must align with the existing angulation of the natural teeth.
In addition, the surgeon may forced to position the implant in the jaw at an angle to a precise vertical orientation. Among the reasons for deliberate angularity are anatomical considerations relating to the volume and quality of the jawbone tissue, as well as the loss of necessary bone support. Thus, the implantologist, in a variety of circumstances may use a range of implant angulations of both the supragingivally extending portion of the prosthetic replacement as well as the portion extending into the bone itself.
The implant procedure initially involves making an incision in the gum tissue to expose the underlying bone.
Next, a initial hole is drilled into the bone to a depth less than the length of the implant. The initial hole diameter is generally significantly smaller in diameter than the ultimate implant diameter. This diameter however, is enlarged during the surgical procedure as successive drilling steps occur. Each step typically includes drilling the hole with a larger diameter drill. This diameter difference allows the implantologist to adjust the final angulation of the implant hole in the bone. The adjustment enables the implantologist to properly orientate the implant and the external prosthetic replacement.
During the surgical procedure, the implantologist commonly uses what is known as a parallel pin or positioning guide to determine the correct orientation of the holes drilled into the bone. The parallel pin includes a pair of pins of different diameters extending outwardly from a transversely oriented annular stop. One of the pins, sized to the initial hole diameter, is inserted into the initial hole until the stop rests on the bone crest. The implantologist can observe the orientation of the supragingivally extending portion of the parallel pin and determine the angle of the hole. If the implantologist determines that the angulation is inappropriate, some adjustment of the hole is still possible as the angulation is adjusted during subsequent drilling steps.
The implantologist must also orient the initial holes for other prosthetic replacements relative to the initial hole already formed. The implantologist commonly uses an implant template which has been prepared in advance to facilitate the placement of other initial holes relative to the first formed hole. The template, for example, will show the correct spacing between adjacent holes.
After the initial hole is drilled, additional drills enlarge the size of the hole. During an intermediate stage of drilling, the second end of the parallel pin is inserted into the intermediate sized hole. The second end has a larger diameter than the first end and, like the first end, is used to depict the angulation of the hole. If the orientation is correct, the final hole is drilled.
The implantologist may have a set of parallel pins, and each parallel pin may have one of a variety of different angles. For example, parallel pins with angles of 0.degree., 15.degree. and 25.degree. may be stocked for a variety of different types of implants and abutment systems. These angled parallel pins may then be utilized in the fashion described above to determine if the correct hole angulation has been achieved. Further, the angled parallel pins may also be utilized with pre-angled abutments.
During an implantation procedure, the implantologist carefully positions implants to have sufficient spacing between adjacent implants and teeth. Generally, for example, the minimum edge-to-edge spacing between adjacent implants is approximately 4 to 6 millimeters; and the minimum spacing between an implant and a natural tooth is about 3 millimeters. Correct spacing is desired to reduce and evenly distribute occlusal forces. In order to accurately position the implants, the implantologist may use an acrylic template or surgical stent.
One disadvantage associated with prior implant system is that an inventory of numerous parallel pins is required. An implantologist, for example, must have a separate parallel pin for each different degree of angulation, such as separate pins for 0.degree., 10.degree., 15.degree., 20.degree., 25.degree. and 30.degree.. The separate pins are costly to the implantologist and require storage space in a surgical kit.
Another disadvantage with prior implant systems is a separate template or surgical stent is required to correctly position implants to adjacent teeth and other implants. These devices are costly and may also require separate storage space in the surgical field.
As another disadvantage, prior art parallel pins are not designed to determine the fit of components of the prosthetic attachment system, such as an abutment. A separate device may be used for such measurements and indications.